1. Field of the Invention
This invention relates to drafting apparatus and, more particularly, to new and novel apparatus for precisely measuring the coordinates of a drawing surface and the location and displacement of a drafting straight edge.
2. Description of the Prior Art
The operation of various machines, such as milling machines, is frequently controlled via computerized machine control systems. The computer programs are defined by X, Y and Z coordinates. The programs which are written for such machines typically start out at an absolute zero point, commonly referred to as ABS.
Heretofore, it has been conventional for a draftsman to construct a drawing of a part to be machined, slavishly calculate incremental movements from point to point about the drawing, and then relate the individual incremental movements to the absolute zero point.
Electronic drafting instruments have been provided heretofore, such as that disclosed in U.S. Pat. No. 4,282,571 issued to Joseph Giovannoli et al on Aug. 4, 1981, which discloses a photo-sensitive device utilized in combination with a microprocessor to continually display the numerical equivalent of a cursor's position on a drafting board. In one arrangement disclosed in the Giovannoli, et al patent, relative positions of a movable cursor selector can be used to determine the length of a line segment by storing the first measured value and subtracting the second measured value. A photo-sensitive device is mounted in such a way that it may slide along an array of cursor segments which are positioned under a movable cursor selector, and in such a way that the lighted cursor segment illuminates a photo-sensitive device.
U.S. Pat. No. 4,184,261, granted to Wolfgang P. Buerner on Jan. 22, 1980, discloses a multi-purpose drafting instrument which utilizes a signal generator in combination with a display unit for measuring and optically displaying the X and Y coordinate values of any selected point within an X-Y quadrant. U.S. Pat. No. 4,246,703, granted to McLouis Robinet on Jan. 27, 1981, as well as U.S. Pat. No. 4,244,105, granted to Constantine Goussios on Jan. 13, 1981, further disclose drafting devices which utilize electronic measuring devices and optical display readouts in combination therewith for measuring displacement of a drafting instrument.
Various devices have been provided for mounting conventional drafting T-squares or drafting straight edges, such as U.S. Pat. No. 694,389 granted to A. Klitsche on Mar. 4, 1902; U.S. Pat. No. 3,864,833 granted to Harold Bokelman on Feb. 11, 1975; U.S. Pat. No. 3,537,183 granted to R. J. Anderson on Nov. 3, 1970; U.S. Pat. No. 1,115,333 granted to H.O. Pease on Oct. 27, 1914; and U.S. Pat. No. 329,392 granted to E. Jordan on Oct. 27, 1885. None of the prior art discloses the concept of combining a slide carrier for a drafting straight edge with a reader head for determing precise measurements and locations of a drafting instrument on a drafting surface. Accordingly, it is an object of the present invention to provide a new and novel drafting straight edge mounting slide carrier which mounts a reader head for determining precise measurements on a drafting board.
It is yet another object of the present invention to provide a new and novel drafting instrument having a drafting straight edge mounting slide which mounts a reader head thereon for measuring coordinates on a mechanical drawing surface.
A further object of the present invention is to provide drafting apparatus including a pair of perpendicularly disposed elongate drafting straight edges and a new and novel mechanism for mounting the straight edges and reader heads for reciprocal to-and-fro movement.
Another object of the present invention is to provide drafting apparatus of the type described, including a carrier block for an elongate drafting straight edge which also mounts a reader head for measuring the location and displacement of the straight edge.
Yet another object of the present invention is to provide new and novel electronic drafting apparatus which will expedite the programming of a computerized machine control for a machine tool.
Still another object of the present invention is to provide new and novel drafting apparatus which comprises a measurement system including a non-contact, photo-optical reader head mounted on a reciprocal slide carrier block which mounts an elongate drafting straight edge.
It is yet another object of the present invention to provide drafting apparatus including a pair of perpendicularly arranged elongate drafting members which overly a drafting table, and mechanism for reciprocally mounting the straight edge members for to-and-fro movement, and mechanism coupling the straight edge members to carrier blocks for selectively clamping the straight edge members to the drafting table to selectively inhibit the to-and-fro movement.
It is another object of the present invention to provide a drafting system which will assist the user to draw any geometric plane, of a part to be machined, showing where and how the part is clamped, the size and type of cutter, the ABS starting point, the central line of tooling path, and any other helpful information that will speed programming and the set-up of equipment.
It is another object of the present invention to provide new and novel drafting apparatus which will assist a draftsman to draw an arc tangent to any side or angle and then plot the center line of the arc for location of the centerline of a machining tool, without the use of calculators and trigonometric functions.
Other objects and advantages of the present invention will become apparent to those of ordinary skill in the art as the description thereof proceeds.